/Engine/Source/Runtime/Slate/Public/Framework/Application/SlateApplication.h
Sets the focus for all users to the specified widget unless that user is focused on a descendant. The widget must be allowed to receive focus.
virtual void SetAllUserFocusAllowingDescendantFocus ( const [FWidgetPath](API\Runtime\SlateCore\Layout\FWidgetPath) & InFocusPath, const EFocusCause InCause )